A conventional seat belt retractor allows a vehicle occupant some freedom of movement, but has a sensor to detect acceleration above a predetermined magnitude indicative of an emergency situation. The seat belt retractor then locks, arresting the vehicle occupant's movement. This can also occur when the vehicle occupant leans forward too quickly to reach a control on the instrument panel. Seat belts which allow movement are desirable for adult vehicle occupants as they restrain passengers in emergency situations but are comfortable because they allow a reasonable degree of freedom for movement during normal driving conditions. When transporting a young child with a child seat the child seat must be fixed in place, but it is desirable for the same seat belt retractor to also operate as a normal inertial retractor to provide the expected comfort for an adult.
This problem is a well known and several solutions have been proposed. U.S. Pat. No. 6,109,556 teaches a seat belt arrangement for motor vehicles, specially adapted for use with a child seat to switch between a fixed mode for the child seat and an automatic mode for adults. Such a seat belt retractor is known as a Child Hold Out Mechanism, sometimes referred to as a “CHOM”.
U.S. Pat. No. 6,109,556 teaches a retractor switching means comprising a cam connected to a spool via a step down gearing arrangement and a cam follower. The step down gearing arrangement comprises an inner gear ring and a gear arrangement with a drive peg located at a predetermined radius. The drive peg is arranged to move cycloidally and rotate the cam when the gear rotates. This cycloidal motion often results in the gear arrangement being known as a “wobble” gear. The cam follower is pivotally mounted and arranged to be in continuous contact with the cam surface. At a predetermined rotational orientation of the cam, the cam follower urges the sensor lever into engagement with a toothed ratchet wheel fixed to the spool to lock the spool and seat belt webbing protraction.
A particular problem with Child Hold Out Mechanism retractors is that a large number of components are needed and this increases the size of the retractor as well as introducing numerous components that generate noise commonly referred to as “rattle noise”.
It is therefore an object of the present invention to provide a noise reducing feature to such seat belt retractors.